Telephone system



Dec. 18, 1928.

I H. M. BASCOM ETAL TELEPHONEYYSYSTEM Filed ApriIZO, 1927 2 Sheets-Sheet EEE Mm? M. 545cm! W flm/rr H 455077 Arm/Mn Dec. 18, 1928. 4

H. M. BASCOM ET AL TELEPHONE SYSTEM Filed April 20, 1927 2 Sheets-Sheet 2 Patented Dec. 18, 1928.

mess-14 UNITED STATES PATENT OFFICE,

HENRY M. BASCOM, OF BROOKLYN, AND HENRY H. ABBOTT, OF NEW YORK, N. Y., AS-

SIGNOBS TO AMERICAN TELEPHONE AND TELEGRAPH'COMPANY, .A CORIPQRA-- TION OF NEW YORK.

TELEPHONE SYSTEM.

Application filed April 2a, 1927. Serial no} 185,241.,

This invention relates to telephone systems, and more particularly to improvements in trunking systems.

According to this invention, a trunking system comprising a plurality of trunks accessible at one end at a first and at a second position and at the other end at a third position is arranged for checking connections over said trunks originating at the first posi- 0 tion and completed through the second and third positions.

According to one feature of the invention, a plurality of acks are arranged at the first position, a plurality of trunks terminating in plugs at the second position and in jacks at the third position, with means responsive to the seizure of a jack at the first position by an operator through a link circuit for connecting said ack through automatic switches to an idle trunk; automatically associates an operators telephone set with said trunk at the second position; establishes a busy condition for said trunk at the third position and ac tuates a signal associated with said trunk at the second position.

A-cording to another feature, means are pr rided whereby when the plug at the secend position is inserted in a multiple jack of the calling subscribers line, the connection to the calling subscriber therethrough is temporarily disassociated'trom the trunk until the calling subscribers line is disconnected from the jack at the first position, at which time the calling subscribers line is reconnected to the trunk by way of said connectionestablished at the second position. I p

The invention may be applied to a so-ealled recording and completing trunking system, in which the recording and completing trunks terminate at oneend in the multiple banks of switches associated with recording jacks l0- cated at A operators positions and in plugs at toll, switching operators positions and,

while at the other end these trunks terminate in jacks atrecording and completing opera tors positions. Connections from calling subscribers that originate at the recording jacks may be checked and completed over the trunks 2m the recording and completing operators positions to the callingsubscriber by way of the toll switching operators positions. I

The invention has been illustrated in the accompanying drawings, as applied to a sys tem of the above mentioned type. Figure 1 shows a calling subscribers line terminating in acks at an A operators position and ,a

toll switchin operators position. It also shows a recording and completing trunk arranged m accordancewlththis invention accessible from the A operators positionand the toll switching operators position andportions of two A operators cords tor connection with the calling subscribers line and the ble over toll line 200, or from such a sub scriber over trunk T to the subscriber of line 1. In establishing a connection from the subscriber of line 1 to the wanted subscriber over toll line 200, the procedure in general is as follows: The subscriber of line 1 calls the operator at A in the usual manner and this operator inserts the answering plug 2 of a cord A at her position into jack 3 01" line 1. and determines the type of connection desired, that is, whether a local subscriber is wanted or a subscriber that may only be reached over atoll connection. 9 The operator also ascertains the calling subscribers number. If a tollconnection is desired, the A operator then tests a multiple recording jack in the. usual manner with plug 4; of another Switches 6 are of the ordinary standard step by-step switches continuously rotating type well known in the-art; The arrangement is such that a plurality of recording jacks like 5 and their associated circuits are normally I associated with individual switches like fi which have their brushes normally resting on .the termlnals of an ldle recording and completing trunk multipled to said switches: .A plurality of such trunks may be connected to these switches of a number larger than the numberot switches and their corresponding recording jacks. WVhen this connection be tween an ,A;operators cord and an idle trunk is completed various actions follow: First, the toll switching operators telephone set (not shown but connected at 10 at the toll switching operators position TS) is automatically connected through switch 6 to the A operators cord; second, a tone, for example, oi the double zip type, is transmitted to the A operators telephone set con nected to the cord 21,, third, the toll switching operators lamp 11 is caused to flash and fourth, the jack of trunk T at the recording operators position at It is made busy. The tone indicates to the A operator that her telephone set is connected through cord A, and switches 6 to a toll switching operators telephone set, and the flashing of lamp 11 indicates to the toll switching operator that her telephone set is connected to an A operators telephone set.

When the A operator hears the tone she will pass the number of a calling subscribers line 1 to the toll switching operator and the toll switching operator thereupon removes her telephone set from the trunk T and iiiserts the plug 1% of trunl; T into the multiple jack 15 of line 1.

lVhen this connection is made the toll switching operators plug 1 1- and associated circuits are temporarily disconnected from the trunk T and the circuits and apparatus associated with the recording jack 5 are actuated to transmit a ringing current impulse over the trunk T which causes a lamp i201 to be lighted at the recording and completing operators position. The recording and com pleting operator new answers this call by inserting plug 20-1 of a cord it into jack 205 of the trunk T. The A operator now gives the recording operator the number of the calling subscriber and disconnects by removing plug 4 of her cord A, from jack 5. She also disconnects plug 2 from jack 3. On the removal of plug 4: from jack 5, the trunk is reconnected to the toll switchin o ierators plug 14 and the associated circuits, while the switch 6 is advanced to connect the re- V by way of toll line 200 by inserting plug 20-1 into jack 208. The connection is now, therefore, completed to the subscriliier of line and the wanted subscriber by way of toll line 200,

trunk T and the connection through the toll switching operators position. This arrangeinent permits the recording and completing operator to check and record the calling subscribers number and to complete the connect-ion to the wanted subscriber.

This recordlng and completing trunk T may also be employed as an ordinary toll switching trunk for calls from the recording and completing operators position to a wanted subscriber through the toll switching operators position. In this case, the toll swi ing operator at TS will be called three by the recording and 00111; without involving the recordi 1 a clts and l be associated circuits and switches. It Slit 1 ll be understood that when a connection of; a type is made, the moment ti'unl; T is talzcn for use theswitches 6 and all other switches associated with recording jacks wil be advanced to connect with the 118K; idle recorc 1,, and completing trunk. These switches will 39 therefore always be ready to connect their spective recording jacks with an idle trunk.

More detailed descriptions will now be made of a connection from the calling subscriber of line 1 to a wanted subscriber over toll line 200 and a connection in the opposite direction. ll hen a toll connection is desired and the A operator has inserted plug t of cord it, into jack 5, an obvious circuit is comple'ted -for the o ration oit relay 1 The operation 01' this relay causes the operation of rclay'lS as follows: Battery, winding of eting oper: or

iii

oit ringing curren: to trunk T in a manner that will be described more fully heroine-l ter. Another obvious circuitii completed from ground at the armature and back contact of relayQO for the operation 0" relay 21. The immediate ci'lect of the operation of relay is to connect the ground at is left hand armature and front contact or this relay to the terminal on which the brush of bani: 2. 3 of switches 6 rests. its this terminal is nuiltipled to the corresponding tern'iinals of all other switches associated with othe re inn; aclts, the brushes of these other sw' will be advanced one step from the teifn'i oi"; trunk T to the terminals of th n t ay 20, let t hand armaturcs and the relays correspondin to the brushes'ot'the contact br corresponding to contact bank 23 th the connected terminal ol? contact ban 1 and the left hand armature and. rent coiita of relay 21 to ground. These circuits cause the relays corresponding to relay 20 to be operated and these relays in opera Q; close ob i-ous circuits tor the stepping magn t. corresponding to the stepping; These stepping magnets will, thei'e'liore, opto advance the brushes o1": ot e 1 idle 'n'iinals. lit the next trunk is busy the step ing magnets will,

s iioncinorback contav relav of course, continue to operate until an idle trunk is found. It is obvious that the brushes of switches 6 will not advance at this time as the corresponding circuit for relay 20 will not be completed.

The operation of relay :21 completes the tip and ringleads from jack 5 through its two outer right hand armatures and front contacts, tern'iinal banlrsv26 and 27 to the tip and ring of trunk T. It will be noted that a circuit to battery and ground is normally connected through the trunk T for normally maintaining relay 210 operated as follows: Battery, right hand winding of relay 29, inner left hand make-before-brealr contacts of relay 30, upper right hand winding of repeating coil 32, upper armature and back contact of relay 3 1, tip conductor of trunk T, upper outer armature and back contact of relay 211, winding of relay 210, lower outer armature and back contact of relay 2-11, ring conductor of trunk T, lower armature and back contact; of relay 34, lower right hand winding of repeating coil 32, left hand winding of relay 29 to ground at the outer right hand make-beforebreak contacts of relay 30. Thus, as stated, relay 210 is normally operated While the electrical characteristics of relay 29 are such that it will normally remain released. hen the above mentioned connection through the two outer right hand armatures andfront contacts of relay 21 is completed, a loop circuit will 6X- tend from the battery and ground at relay 29 throught-he low resistance of the retardation coil 36 and cause relay 29 to operate while relay 210 is released. That is the ci-rcuit through the winding of relay 210 is shunted by the low resistance circuit through retardation coil 39.

Relay 210 in releasing establishes a con nection from battery at the armature and back contact of relay 212 through a resist ance 213, the upper inner armature and back contact of relay 211, armature and back contact of relay 210 to a point between the resistance 21 1- and ground and the Winding of relay 215. Thus, as the other end of the.

winding of relay 215 is connected to the sleeve of pick 205, a busy condition isestablished on the sleeve, so that the trunk T will.

test busy to any recording and completing operator attempting to establish a connection over this trunk. v Y

Relay 29 inoperating connects ground to one side of the right hand winding of relay 30. Practically simultaneously a ground is connected atthe left hand armature and front contact of relay 21 so that these ground connections cause the operation of relay- 30 and the lighting of lamp 11 over a circuit as follows: Battery, lamp 11, lower armature and back contact of relay 37, right hand winding of relay 30, armature and front contactof relay 29 to ground orto the ground at the left hand arn'iature and front contact of relay 21. The operation of relay 30 opens the connections to battery and ground for the windings of relay 2 through its makebefore-break contacts to the retardation coil 32, but relay 29 is maintained operated by the operation of relay 30 over a circuit from battery through the right hand winding of relay 29, inner right hand armature and front contact of relay 30 to ground. The lighting lamp 11 is of no particular importance at this time, except to warn "the toll switching operator that a connection may be desirable through this trunk.

it should be noted that the ground at the armature and front contact of relay 29 and the ground at the left hand armature and front contact of relay 21 are connected for the operation of relay 39 overa circuit/as follows: Battery, lower winding of relay 39,

per inner armature and back contact of 1 relay 1O to said grounds. Relay 39 in operating closes a circuit to ground for lead 41 at its lower armature and front contact. This connection to ground causes the toll switching operators telephone set to be con-. nected through leads 12 and 13 to the trunk T and causes an intermittent battery connection to be made through lead 1 1 for the flash ing of lamp 11. It also causes a tone of the double zip-type to beapplied to a lead 42. The circuits for accomplishing these functions form no part of this invention but are illustrated completely in the Patent No. 1,685,338, toWViley lVhitney. Leads 12, 4.3, 4:1, 4% and 45 of the present application correspond respectively to leads 12, 13, 10, 9 and 11 in Fig. 1 of the Whitney application. The double zip tone applied to lead 42 is transmitted over the ring conductors through the repeating coil 32 to the A operators telephone set of cord A, to indi' cate to this operator that the toll switching v operators telephone set has been connected to the trunk, while the flashing of lamp 11 in dicates to the toll switching operator that her telephone set has been connected to this particular trunk. The operation of relay 30 applies a ground at the outer right hand armature and front contact through the upper inner armature'and front cont-act of res lay so that a circuit will now be completed from battery through the lower winding of relay 4:0 and upper winding of relay 39, to this ground. This circuit causes the operation of relayO and maintains relays 40 and 39 in operated condition as long relay 30 is operated. The operation of relay 40 opens at itsiupper inner armature and front conof the calling subscriber to the toll switching operator and the toll. switching operator thereupon inserts plug 1i into ack 5 or this calling suhscrihefls line 1. l owevcr, previous to the insertion of this plug into gaclr 15, she will operato'a key to remove her telephone set from the trunk. in accordance with the above mentioned copending application to ll iley l l hitney, a ground Will he connee-ted under these circiunstances to lead L5, which as stated corresponds to lead 11 ot' the ll hit-ney application. This ground maintains relay l0 energized through the lower Winning, hut short-circuits the upper Winding of relay 39 so that this latter relay will new release. On the release of this relay a circuit will be completed as soon as plug 1% is inserted inja h and relay 3'? is energized through the sleeve circuit, to cause the lamp ll to be shortcircuited as follows Battery through the upper outer armature and leach contact of relay .39 upper outer arrnature and front contact of relaydt), low resistance it) high resistance l? to ground. it this circuit had not been closed the filllg 11 would he lighted steadily on the operation of relay 3'? through the circuit established at its lower armature and front contact to ground through the high resistance 15. lit the lamp 11 had lighted steadily through this circuih it would have indicated to the toll switching operator th she had neglected to remove her telephone set from the trunk.

The opci tion of relay 3'? opens the above mentioned holding circuit for relay but as the subscriber off line 1 has already removed l s receiver from the hook a circuit will be con'ipleted through the tip and ring conductors of the trunk and the left hand windings of repeating coil 32 through the winding; of the relay 49 so that relay ll? in operating Wl ll niaintain relay 3O operated over a circuit from battery to the left hand Winding of relay 30, armature and front contact of relays-9 right hand Winding" of relay 30 to ground at the armature and front contact of relay 29.

lt- Will be noted that when relay 30 first operuteth a circuit was completed for the operation of relay as follows: Battery Winding of relay 50, nialre-hefore-hrer contacts of this relay through the inner right hand armature and front contact of relay 21,tern1ina l bank 51, outer rih ht hand armature and trout contact of relay to ground. I clay 50 in operating opens itsenergizi circi hut completes a locking circuit for itse through itsripght hand armature and front contact to ground at the armature and heel: contact of. relay 201 Relay 50 in operating thus prepares a path for the operation oi relay 52, which is completed on the insertion of plug 14: into jack 15 as follows: Battery, winding of relay 52., left hand armature and front contact of relay 50, terminal haul: sleeve terminals or plug 14: and jack 15 to ground. Relay :32 in operating closes an obvious circuit for the operation of relay 19 to the ground at the armature and back contact of relay T he operation of relay 19 completes a circuit from a source of ringing currentat 53 through the arinaturos and front contact of relay 18 and upper and lower outer arinatures and "front contacts oi relay 19 to the tip and ring conductors of trunk 10. The energizing circuit for relay 18 is open on the ope 'ation of relay 19,hut as relay 1% is slow to release, short impulse of ringing current from source will now he applien to the tip and ring terminals of trunlr T. This inipulse Will he received at the recording; and completing operator's position to worsentarily operate the ringing relay 218. Relay 5218 in operating: closes a holding; circuit for itself and also a circuit through its armature lrtront contact for the operation of relay to the ground at the inner lower arinature and back contact of relay The relay was connected as hereinheiore stated, for inakin aclz 205 husy. Relay 212 in operating); col. pletes a circuit for this hattery tor the lighting of lamp 201 to indicate to the recording and completing operator that a connection is desired over this trunk.

The recording and completing}; operator at ll now inserts plug; 204 into jack 205 and thus causes the operation of relay 215. This relay in operating closes an obvious circuit for the operation of relay 211 and this relay in operating removes the relays 210 and 218 tronracross the tip and ring; terminals of the trunk and causes the release of relays 212 and 218 so that the tip and ring conductors are now clear of these lorid normally connected. across these conductors. The A operator Will noW comnuinicate with the recordingoperator and give her the number of the Calling subscriber: andthen remove her plus o't cord A ttroin iaclr 5. The A. operator will also reniove plug 0t cord from aclr. 3 at this time It should he noted that after relay has operated and relay 1% h ole Fil a talking; connect-ion is comp weted from t1 e A operator to the recording operator over the tin and ring; conductors connected at t e armatures and hack contacts ofrela-y 18 an d upper and lower outer armatures and front contacts of relay 19.

lit should also he observed that when ro -v 19 operates acireuit com leted tor the operation of relay 34-, as follows: llattewc lovver inner arinature and front contact oi relav 1!) terminal haul?v windino of relay 341 to .o roun'd. Relay 3A. in operaiine toniporarily disconnects the tip and rin conductors of the trunk 'i from th p and ring conductors leadii through eatino; coil to the call S11l35C1ll,)01"S line over plugr l4: and aclz: 15, so that when the reco ding and completing operator is called, ring- 21:2 in operating removes the battery that tip tion is dos ing current will not be transmitted to the calling subscriber and so that whenthe A operator passes the number or the calling subscriber to the recording and completing operator, the toll switching operator and the calling subscriber will not be involved.

On the removal of the plug 4 from jack5 relay 17 releases which in turn causes the idle trunk. The release of relay 19 will, of

course, cause the release of relay 34, so that a connection will now be completed between the calling subscriber of line 1 tl'irough the toll switching operators position TS over trunk T to the recording operators position at R. The recording and completing operator now asks the calling subscriber for his ovn number and the number of the wanted subscriber and then completes the connection. through plug 207 and jack 208 to the wanted subscriber over toll line 200 in the usual manner. lVhcn this connection is completed and the wanted subscriber has been called in I the usual manner, conversation between the calling subscriber and the called subscriber may take place. Thus the connection may be checked, recorded and completed by the reeordin and completing operator.

if trunk T is used as an ordinary toll switching trunk for calls originating at the recording and completin operators position, therecording and completing operator will after having received the call from a subscriber over toll line 200, insert plug 204 in jack 205 to extend the connection through to the wanted subscriber. The immediate efiect of this connection will be the operation of relay 215 and relay 215 in operating completes n obvious circuit for relay 211. Relay. 211 clears the tip and ring conductors from the bridged relays 210 and 218. The

through from the recording and completing operator. cord to battery and ground through the windings of relay 29. This causes relay 29 to operate and apply ground at its armature and front contact for the connection of the toll switching operators tele 1 1 I 0 pnone to the trunk as hereinberore described and also to cause lamp 11 to flash to indicate to the toll switchin o aerator that aconnecover this trunk. The ground at the armature and front contact of relay 29 is also applied tl'irough the associated terminals of terminal bank 23 and all other. coraud ring conductors are connected responding banks, thus making switch 6; and

all the otherswitches advance to the next. idle trunk. The operationof relay 30 onthe operation of relay 29 removes, as is. evident, battery and ground from the tip and ring conductors of the trunk T,

After the toll switching operator has re ceived the number of the wanted subscriber, she will cause her telephone set to be removed from the line, as hereinbefore described, and insert plug'14 in jack 15 of the desired sub-v scribers line 1. This connection causes the operation of relay 37 and the circuit for relay 30 is thereby opened so that this relay,

when releasing will again connect battery and ground to the tip and ring conductors through the windings of relay 29. This con--1 nection causes the usual supervisory signal at the recording and completing operators cord R to be lighted, indicating to this operator that she may ring the wanted subscribers line. In applying ringing current to the trunk T in the usual manner relay 57 will operate. The operation of this relay closes an obvious circuit for the operation of relay 58. It will be noted that the circuit for relay 58 also extends from battery through the left hand winding of relay 30, so that relay 30 will operate at this time to prevent relay 29 from releasing during ringing. Relay 58' in operating applies ringingv current to the wanted subscribers line. When the called subscriber answers by removing the receiver from the hook, relay 49 will operate as soon as the recording and completing operator ceases ringing and this relay in operating will complete a circuit. for maintaining relay 30 operated. from battery through the left hand winding of relay 30, armature and front contact of relay 49, right hand winding of relay 30 to ground at the armature and front contact of f This circuit may be traced" wanted subscriber has answered. Conversation between the called subscriber of line Y 1 and the calling subscriber of line 200 may now begin.

WVhen the called subscriber hangs up his receiver on the hook, relay 49 releases causing the release ofrelay 30 and thus causes a supervisory signal to be given at cord R and the recording and completing ope'ratormay now take down the connection by removing plugs I 204 and 207 from jacks 205 and 208, respec tively, Upon the removal of plug 204 from 'ack 205 relays 215 and 211 will release to ridge relays 210 and 218 across the line, causing the release of relay 29. Relay 29 in releasing causes the release of relay 40 and the short-circuit from lamp 11 is thus removed so this lamp now lights to indicate to the toll switching operator that disconnection is desired. The toll switching; operator by removing plug i l from jack 15 causes the re turn of the circuit at this end of the trunk to normal.

It should be understood that the trunking system described in this specification is merely illustrative of one application of the invention and that the various features oi the invention may readily be adapted to other systems having similar traffic conditions to meet without departing from the spirit of the invention.

What is claimedis:

1. In a telephone system, a trunk accessible at one end from a first operators position and terminating at the same end at a second operators position and at the other end at a third operators position, a s'ubscribers line having connecting terminals at the first and second positions, a link circuit at the first position for connection with said trunk, means responsive to the connection of said link circuit with said trunk for signaling the operator at said second position and for establishing a busy condition on the trunk at said third position, means for connecting said trunk and said subscrihers line at said second position, a signal at the third position, means responsive to said last mentioned connection for actuating said signal and for telephonically disconnecting said subscribers line at said second position from said trunk, and means responsive to the release of said trunk from said link circuit at the first position "for reconnecting said subscrihers line telephonically at said second position to said trunk.

2. In a telephone system, a trunk accessible at one end from a first operators position and terminating at the same end at a second operators position and at the other end at a third operators position, a subscribers line having connecting terminals at the first and second positions, a link circuit at the first position for connection with said trunk, an operators telephone set at the second position, means responsive to the connection of said link circuit with said trunk for signaling the operator at the second position for establishing a busy condition on the trunk at the third position and for automatica ly connecting said. operators telephone set to said trunk at the second position, means iorconnecting said trunk and said subscribers line at the second position, a signal at the third position, means responsive to said last mentioned connection for, actuating said signal and for telephonically disconnecting said subscribers line at the second position from eonora said trunk, and means responsive to the rclease of said trunk from said link circuit at the first position for reconnecting said subscribers line telephonically at the second po sition to said trunk.

8. In a telephone system, a first, a second and a third operators position, a plurality of trunks, one end of said trunks terminating at the second position in individual connecting terminals and at the other end the third position in individual connecting terminals, a plurality of sets of connecting terminals at the first position, an automatic switch associated with each set of connecting terminals at the first position, a subscribers line having connecting terminals at the first and secondpositions, a link circuit at the first position for connection with any set of connecting terminals at this position, means responsive to the connection of said link circuit with one of said sets of'connectin terminals at the first position for automatically connecting said set of connecting terminals with an idle trunk through the associated switch, means for connecting said seized trunk and said subscrihers line at said second position, a signal at the third position vassociated with each of said trunks, means responsive to the establishing; oi said last' sive to the release of said set of connecting terminals at the first position from said link circuit for disconnecting said set of connecting terminals from the trunk and for reconnecting said subscrihers line telephonically at the secondposition to said trunk.

i. in a telephone system, a first, a second and a third operators position, a plurality of trunks, one end of said trunks terminat ing at the second position in individual con necting terminals and at the other end at the third position in individual connecting terminals, a plurality of sets of connecting terminals at the first position, an automatic switch associated with each set of connect ing terminals at the first position, a subscribers line having connecting terminals at the first and second positions, a link circuit at the first position for connection with any set of connecting terminals at the first position, means responsive to the connection of said sets of said link circuit with one of connecting terminals at the first position for automati cally connecting said set of connecting terminals with an idle trunk through the associated switch, means for connecting said seized trunk and said subscribers line at the second position, a signal at the third position associated with each of said trunks, means responsive to said last mentioned connection for actuating the si 'nal at the third position associated with said seized trunk and for telephonically disconnecting said subscrihers line at the second position from said trunk, and means responsive to the release said set of connecting tern'iinals at the first position from said link circuit for disconnecting said set of connecting terminals from said trunk and connecting the associated switch with the next idle trunk and for re connecting said suhscrihers line telephonically at the second positionto said trunk.

5. In a telephone system, a first, a second and a third operators position, a plurality of trunks, one end of said trunks terminating at the second position in individual con necting terminals and at the other end at the third position in individual connecting terminals, a plurality of sets of connecting terminals at the first position, an automatic switch associated with each set of connecting terminals at the first position, a subscrihers line having connecting terminals at the first and second positions, a link circuit at the first position for connection with any set of connecting terminals at the first position, means responsive to the connection of said link circuit with one of said. sets of connecting terminals at the first position for automatically connecting said set of connecting terminals with an idle trunk through the associated switch and for connecting the associated switches of the remaining connecting terminals at the first position with the next idle trunk, means for connecting said seized trunk with said suhscribers line at the second position, a signal at the third position associated with each of said trunks, means responsive to said last mentioned connection for actuating the signal at the third position associated with said seized trunk and for telephonically disconnecting said subscrihers line at the second position from said trunk, and means responsive to the release oili said sets of connecting terminals at the first position :lrom said link circuit for discon necting said set of connecting terminals from the trunk and for reconnecting said subscribers line telephonically at the second position to said trunk.

6. In a telephone system, a first, a second and a third operators position, a plurality oi trunks, one end of said trunks terminating said i ct of connecting terminals with an idle through the associated switch, for signaling the operator at the second position and for establishing a busy condition on the seized trunk the third position, means tor connecting said seizedv trunk and said subscrihers line at the second position, a signal at -the third position associated with each of trunks, means responsive to said last at the third position associated with said seized trunk and for telephonically disconnecting said suhscrihers line at the second position from said trunk, and means responsive to the release of said set of connecting terminals at the first position from said link circuitfor disconnecting said set of connecting terminals from the trunk and for reconnecting said subscrihers line telephonically at the second position to said trunk.

7. In a telephone system, a trunk accessible at one end from a first position and terminating at the same end at a second position and at the other end at a third position, sets of connecting terminals at the first position, automatic switches associated with each set oi connecting terminals andhaving access to said trunk, a subscrihers line terminating at the first and at the second position, a link circuit at the first position for connection with any set of connecting terminals thereat, means responsive to the seizure of a set of connecting terminals by said link circuit for automatically connecting said set of terminals to the trunk through the associated switch for signaling the operator at the second p0sition and -for establishing a busy condition at the third position, means for connecting said trunk with said suhscrihers line at the second position, a signal atthe third position, means responsive to the establishing of said last mentioned connection for operating said sig nal and telephonically disconnecting said subscrihers line from said trunk at the second position, and means responsive to.the release of said set of connecting terminals through the link circuit at the first position for disassociating said set of connecting terminals from the trunk and for reconnecting said subscrihers line telephonically at the second position to said trunk.

8. In a telephone system, a trunk accessible at one end from a first position and terminating at the same end at a second position and at the other end at a third position, means for establishing a telephonic connection from the first to the second position and from the first to the third position, a subscrihers line, means for connecting said subscribers line to said trunk atthe second position and prevent ing telephonic connection to the second position over the trunlnand means for reestab- '75 mentioned connection for actuating the signal lishing telephonic connection to the second position over said trunk from the third posi tion only.

9. In a telephone system, a plurality of trunks accessible at one end from a first position and erminating at the same end at a second position and at the other end at a third position, a plurality of switches, means for establishing a teieohonie connection over any one of said switches from the first position to an idle t1111'll,1112111$ for telephonicelly Initiating at the second position, and means for disabling the telephonic connection from V the first position to the trunk and reestablishing the. telephonic connection to the second position over the trunk.

In testimony whereof, We have signed our names to this specification this 19th day of April 1927.

HENRY M. BASCOM. HENRY H. ABBOTT. 

